1

Performance aspects of the instrument

M. Bertaina

Univ. Torino & INFN

EUSO Balloon Phase A Review Meeting, CNES Toulouse, February 2nd 2012

2

Functional Requirements• R-4.1-1 Background imaging

The Instrument shall image the UV sky background in the bandwidth used by the JEMEUSO mission observational technique.The background includes star light, airglow, light from artificial sources.

• R-4.1-2 Detection of EASThe Instrument shall trigger, detect and image EAS with energy above 1018 eV that might develop in the field of view.

• R-4.1-3 Technology demonstratorAll key components and the relative sub-assembly items should be tested according to the configuration foreseen for the JEM-EUSO mission.This is needed to test the JEM-EUSO detection technique.

From: EUSO BALLOON INSTRUMENT Technical Specification documentDocument: EUSO-TS-INST-206-LAL V1.0

3

On the Sky BackgroundNightglow background: 100 - 500 photons/m2/ns/sr

Sakaki, BABY, NIGHTGLOW, Tatiana increases by ~1.5 with clouds

Airglow (~100 km height): 250 - 600 photons/m2/ns/srMoon phases (<25%): <100 ph/m2/ns/sr

500

1000

2000

From Tatiana Universitetsky Satellite. and = large cities

ph/m2/ns/sr

Background measurements with coarse resolution (~200 km FoV)

4

BABY vs Tatiana: with reduced FoV higher fluctuations are expected

O.Catalano et al.,NIMA 480 (2002) 547

Balloon trajectory

EUSO-Balloon:

a) will have finer resolution at ground (~200m)

b) will implement a control on background variations to keep a stable trigger rate (~7 Hz)

5

SWITCHES LOGIC AND BRIGHT EVENTS (TLEs)TLE jet

Power 104 W

Duration 0.4 s

Radius 40 km

Height in atm.

Troposphere

NO SWITCHES

WITH SWITCHES

THE SIGNAL HAS BEEN SAMPLED: THE INTERVAL BETWEEN 2 GTUs IS 1 ms!!!

250 pC

0 s 0.4 s

250 pC

The logic of switches of EUSO-Balloon will be tested to verify:

a) Capability of protecting the detector from bright events

b) Measure their light curve and intensity

6

The observation principle of JEM-EUSO

Simulation of the light profile observed at the entrance pupil (above) and throught the instrument

using the ESAF code

duration ~ 50 – 150 s

7

PARAMETERS OF EUSO-BALLOON COMPARED TO JEM-EUSO

JEM-EUSO EUSO-Balloon

Height(km) 420 40

Diameter(m) 2.5 1

FoV/pix(deg) 0.08 0.25

Pixel@ground(km) 0.580 0.175

FoV/PDM(deg) 3.8 12

PDM@ground(km) 28.2 8.4

Signal Ratio 1 17.6

BG Ratio 1 0.9-1.8

S/N 1 20-10

Ethr(eV) 3x1019 1.5-3x1018

Number of PDM 143 1

Maximize performance of EUSO-Balloon keeping parameters as close as possible to JEM-EUSO

8

First assessments on the EAS observation by EUSO-Balloon

A) Shower simulator SAITAMA Code, version Sato – 2005)B) Ray trace code version Takky – 07112011C) Flat PDMD) M64 PMT simulation as in JEM-EUSO M64E) Trigger module as in JEM-EUSOF) Average nightglow background adapted to EUSO-Balloon

(1.4 - 2.8 phe/pix/GTU)G) Accepted fake trigger rate ~7 Hz

Simulation inputs:

R=4.2kmR=4.2km

R=10km

EAS impact point at ground simulated at distances R < 10 km around the Nadir of the telescope.

9

Typical event observable by EUSO-Balloon (1)phe/GTU

Time(GTU)

Time(GTU)

Time(GTU)

Xp

ix

Yp

ix

Yp

ix

Xpix

Proton:

E = 2·1018eV = 49.0= 213.0X0 = 3.0 kmY0 = 2.9 km

ph

e/G

TU

Event landing in the FoV

10

phe/GTU

Time(GTU)

Time(GTU)

Time(GTU)

Xp

ix

Yp

ix

Yp

ix

Xpix

Proton:

E = 4·1018eV = 57.5= 188.7X0 = 9.3 kmY0 = 3.1 km

ph

e/G

TU

Event landing outside the FoV

Typical event observable by EUSO-Balloon (2)

11

GTU = 1 GTU = 2

GTU = 3 GTU = 4

X(pix)

Y(p

ix)

Proton:

E = 4·1018eV = 57.5= 188.7X0 = 9.3 kmY0 = 3.1 km

<Background>:1.4 phe/pix/GTU

phe

Simulation of event (2) GTU by GTU with background

12

GTU = 5 GTU = 6

GTU = 7 GTU = 8

X(pix)

Y(p

ix)

Proton:

E = 4·1018eV = 57.5= 188.7X0 = 9.3 kmY0 = 3.1 km

<Background>:1.4 phe/pix/GTU

phe

Simulation of event (2) GTU by GTU with background

13

GTU = 9 GTU = 10

GTU = 11 GTU = 12

X(pix)

Y(p

ix)

Proton:

E = 4·1018eV = 57.5= 188.7X0 = 9.3 kmY0 = 3.1 km

<Background>:1.4 phe/pix/GTU

phe

Simulation of event (2) GTU by GTU with background

14

GTU = 13 GTU = 14

GTU = 15 GTU = 16

X(pix)

Y(p

ix)

Proton:

E = 4·1018eV = 57.5= 188.7X0 = 9.3 kmY0 = 3.1 km

<Background>:1.4 phe/pix/GTU

phe

Simulation of event (2) GTU by GTU with background

15

GTU = 17 GTU = 18

GTU = 19 GTU = 20

X(pix)

Y(p

ix)

Proton:

E = 4·1018eV = 57.5= 188.7X0 = 9.3 kmY0 = 3.1 km

<Background>:1.4 phe/pix/GTU

phe

Simulation of event (2) GTU by GTU with background

16

Energy(eV)In

teg

rate

d N

. E

ven

ts [

1018

,E]e

V i

n 1

0h

LEFT PLOT: Trigger efficiency curve for events with impact point inside FoV.RIGHT PLOT: Black, red and blue curves give preliminary results on the performance from a 10 h duration flight for different assumptions of background and cosmic ray flux.

7 Hz/PDM

Tri

gg

er e

ffic

ien

cy (

%)

Energy(eV)

Efficiency=1 & 1.5 x Aug. fluxEfficiency=1 & Auger fluxEB & A.fl. & <B>=1.4 pheEB & 1.5xA.fl. & <B>=1.4 pheEB & A.fl. & <B> =2.8 phe

EUSO-B. & <B>=1.4 phe/pix/GTUEUSO-B. & <B> =2.8 phe/pix/GTU

● 80 Hz fake trig.o 7 Hz fake trig.

17

CONCLUSIONS• EUSO-Balloon will IMAGE the UV sky background (star light, airglow,

TLEs, artificial lights) in the bandwidth used by the JEMEUSO mission observational technique.

• All key components and the relative sub-assembly items will be tested according to the configuration foreseen for the JEM-EUSO mission.In particular the trigger scheme and its capability to cope with the variable sky conditions (EXTREMELY IMPORTANT).

• A first simulation study has been performed to understand the effective energy threshold of EUSO-Balloon and its possibility to detect showers in a 10h flight.

• Results confirm the capability of the instrument of detecting primary cosmic rays of energy E>1018 eV.

• Due to the low cosmic ray flux the detection of a couple of events will require few days exposure time (dependent on the sky background condition), therefore the detection of the first air shower from the edge of the space will most probably require more than one flight.